Carrier-current signaling system



1,640,550 1927- D. G. LITTLE CARRIER CURRENT SIGNALING SYSTEM Filed April 2, 1924 ///////////////fl/////fl/ WTN ESSESZ NVENTOR Dona/da Liti/e ATTORNEY Patented Aug. 30, 1927.

UNITED STATES' PATENT OFFICE.

HOUSE ELECTRIC 86 MANUFACTURING VANIA.

COMPANY, A CORPOBATION OF PENNSYL- CARBIER-CURBENT SIGNALING SYSTEM.

Application filed April 2,

This invention relates to radio-frequency systems for signaling over line conductors. Particularly, it relatcs to signaling by means of carrier currents.

It is an object of this invention to take advantage of the properties of standing waves, such as are produced in long lines by the application of high-f'equency energy thereto.

It is a further object of this invention to prevent interference by the standing waves by locating the sgnal-receiving apparatus at a node of the standing waves established by the sending apparatus.

By making use of' two sets of standing waves, si'nultanedus signaling in two directions over the same wire may be accomplished. The signal-sending apparatus and the signal-receiving apparatus at the same station are separated by a quarter-wavelength of the energy from the sending apparatus at that station. consequently, the receiving apparatus is at a node of these waves.

lVhile my invention is directed primarily to the location of potential-responsive appa'atus at the nodes of such standing potential waves, the location of current-responsive apparatus at the nodes of current waves also comes within the scope of my invention.

The invention may be better understood by reference to the following description and the accompanying drawing, in which the single figure is a diagram illustrating the principle thereof.

The invention is illustrated as applied to a line 1, which may, for example, be a transmission line, that is parallel to the ground 2, but it s equally applicable to a plurality of lines, and to a completely metallic circuit, whether or not it is grounded.

At one station, the sending apparatus 3 comprsng means for generating and modulating high-frequency energy, is connected to the line 1, referably by means of a condenser 4. This enables the line 1 to be used for purposes other than signalng. It may, for example, serve as a power line. The energy delivered to the line 1 by the sending device 3 will give rise to standing waves which are diagrammatcally represented by the curved line 5. Assuming that the Sending device .3 is of a type which causes poten- 1924. Serial No. ?03,668.

The invention is equally applicable to sending apparatus which inpresses current upon the line. In such an application, the curve 5 will represent a standing currentwave and the connection would be either direct or by means of a transformen' The cu'ves in the figure show but a single wave length between Stations. In the practice of the invention, the distance will usually be more than this and, often, it may be many times as great.

The wave represented by the line 5 will have a loop at the sending apparatus 3, al though this apparatus need not be at the exact center of the loop. N odes of the wave represented by the line 5 occur at half-wavelength intervals along the line 1. At the point 6, which is one of these nodes adjacent to the sending device 3, a receivng device 7 is connected to the line. This connection is illustrated as made by means of a condenser 8, but other ways of making the connection are contemplated.

Because the point 6 s a node of the waves 5, little energy from the sending device 3 reaches the 'receiving device 7 The receiving device, is theret'ore, unafi'ectcd by the adjacent sending device, ?and the signals sent from the device 3 do not inter-tere with reception of other signals by the receiver 7.

The sending device 3' and the receiving device 7, together constitute a station. A second station, having a sending device 9 and a receivng device 10 that are connected to the line 1 by condensers 11 and 12, respectively, is represented in the drawing. The connection to the sending device is shown at a node of the wave 5, but this location s not a necessary feature of the sysem. It is however, desirable, because the Wave 5 Will be less distorted by the sending device 9 if the connection to the line is made at a node.

The standing wave on the line 1, caused by energy from the sending device 9, will have a loop adjacent to the connectionto this sending device, 'although the connection generally will not be at the exact center of the loop. This standing wave is represented by the curve 14. This wave has nodes at each half-wave-length, of course,

but its wave-length is not necessaril (r usually the same as the wave-length o the standing wave represented by the curve 5.

The connection to the recevin device 10 is located at a qu'arter-wave-lengt from the sending device 9 so that the energy from the sending device 9 cannot afiect the receiving device 10.

The wave-lengths of standing waves upon a line depend upon the frequenoyand upon the characteristicsof the line. The distributed inductance and distributed capacity are the characteristics of the line which have the greatest effect upon the length of the standing waves. These characteristics are very nearly constant; consequentl once the instruments have been tuned, furt er adjustment is not needed.

It is evdent that, when geographical considerations fix the distance between a sending device and its neighboring receiving device, this distance may bemade a. quarterwave-length by adjustment of the frequency.

It will be evident to those skilled in the art that my invention is not limited to the use of only two sets of standing waves and also that many variations of detail, beside those explcitly mentioned above; may be made without departing from the spirit of this invention, which is not limited except as required by the prior art or indicated in the claims.

I claim as my invention:

1. A carrier-current system of radio frequency signaling comprising a transmission line and a plurality of sending and receiving Stations, each of said Stations comprising a sending' apparatus adapted to excite said transmssion line by producing ,stationary loops and nodes ofhigh-frequency potential thereon and each station also comprising a receving apparatus energized from said transmission line at a point which is a potential node for the energy delivered by the sending apparatus of the same station, and not a potential node for energy delivered by the sending apparatus of another station.

2 In a high-frequency signaling system, a line, two signal-sending devices for impressng hgh-frequency energy upon said line at a distance apart greater than a halfwave-length and a receiving device adjacent each signal-sending device',' each signal-receiving device being at a quarter-wavelength from the adjacent signal-sending devce.

3. In a high-frequency signaling system, a line, a signal sending device for impressng high-frequency energy'upon the line to cause standing waves thereon, an adjacent sgnal-receiving device ata quarter-wavelength from said signal-sending device and a istant signal-receiving device at approximately an even number .of quarterwave-lengths from said signal-sending device Whereby the neighboring signal-receiving device will be insensitive to the energy sent out by said sending device and the dstant signal-receiving device will be responsive to said energy. I

4. In a high-frequency signaling system, a line, two signal-sending devices for impressing high-frequency energy upon said line at a distance apart greater than a halfwave-length, two signal-receving devices,

each at a quarter-wave-length from the ad-' jacent signal-sending device and at approximately an even number of quarter-wavelengths from the distant signal-sending device, whereby each signal-receiving device is insensitive to the energy fromthe adjacent signal-sending device and' responsive to the energy from the distant signal-sending device' In testimony whereof, I have hereunto subscribed my name this QTth day .of March, 1924.

DONALD G. LITTLE( 

